GPU core temps and overclocking

So i was tweaking my
Nvidia Geforce 6800 xt the other day using riva tuner and

well i deceded that maybe i was pushing it wen the core temp was 82* celcious. durring a bit of gamming

im just wondering if anyone has any input about whats a safe temp for the core to be @ . The card is getting a little slow for the stuff that im doing and i just want a bit more performance.
It idles @ 54 degrees